Strange problem when posting via news.gmane.org

I'm having a strange problem posting to *some* newsgroups on
news.gmane.org with tin.

I *can* post to gmane.test using tin, and I can post to a couple of
other groups.

However when I try to post to any of the following groups:-

    gmane.org.clubs.dba.bargelife
    gmane.org.clubs.dba.general
    gmane.org.clubs.dba.waterways.ce
    gmane.org.clubs.dba.waterways.gb

using tin the posting fails and I get an error mailed back to me by
the DBA with the following:-

    Hello Chris Green

    A posting sent to the forum contains a blank subject and the
    message:  - 'Barge Life'.

    This is an automated email. If you are having difficulty, please
    contact us at [email protected]


However if I post using thunderbird the posting works perfectly!

So, what's tin doing so differently from thunderbird?

(By the way I posted from both tin and thunderbird using a direct NNTP
connection to the gmane server at news.gmane.org)

-- 
Chris Green